Various organometallic precursors are used to form high-κ dielectric thin metal films for use in the semiconductor industry. Various deposition processes are used to form the metal films, such as chemical vapor deposition (“CVD”) or atomic layer deposition (“ALD”), also known at atomic layer epitaxy.
CVD is a chemical process whereby precursors are deposited on a substrate to form a solid thin film. In a typical CVD process, the precursors are passed over a substrate (wafer) within a low pressure or ambient pressure reaction chamber. The precursors react and/or decompose on the substrate surface creating a thin film of deposited material. Volatile by-products are removed by gas flow through the reaction chamber. The deposited film thickness can be difficult to control because it depends on coordination of many parameters such as temperature, pressure, gas flow volumes and uniformity, chemical depletion effects and time.
ALD is a chemical process which separates the precursors during the reaction. The first precursor is passed over the substrate producing a monolayer on the substrate. Any excess unreacted precursor is pumped out of the reaction chamber. A second precursor is then passed over the substrate and reacts with the first precursor, forming a second monolayer of film over the first-formed film on the substrate surface. This cycle is repeated to create a film of desired thickness. ALD film growth is self-limited and based on surface reactions, creating uniform depositions that can be controlled at the nanometer-thickness scale.
Govindarajan, S., et al. reports rare earth doping (Ge, Er, Dy) of HfO2. Hf, Zr and rare earth dopant were deposited with physical vapor deposition. [“Higher permittivity rare earth doped HfO2 for sub-45-nm metal insulator-semiconductor devices,” Applied Physics Letters. 2007. 91:062906]
Yashima M., et. al. report zirconia-ceria solid solutions and lattice in an abstract presented at the Fall Meeting of the Ceramic Society of Japan, Kanazawa, Japan, Sep. 26-28, 1990 (Paper No. 6-3A07), and at the 108th Annual Meeting of the Japan Institute of Metals, Tokyo, Japan, Apr. 2-4, 1991 (Paper No. 508).
Scott, H. G. reports metastable and equilibrium phase relationships in zirconia-yttria system. [“Phase Relationships in the zirconia-yttria system,” J. Mat. Science. 1975. 10:1527-1535].
International Publication No. WO 02/27063 reports vapor deposition processes using metal oxides, silicates and phosphates, and silicon dioxide.
Zirconia, hafnia and TiO2 have been used to create dielectric films, generally to replace silicon dioxide gates for use in the semiconductor industry. Replacing silicon dioxide with a high-κ dielectric material allows increased gate capacitance without concomitant leakage effects.
Therefore, methods are needed to create and improve high-κ dielectric films by either increasing the dielectric constant, or stabilizing the film to maintain a high dielectric constant, or both.